I'd just like to interject for a moment. What you're refering to as Android, is in fact, Busybox/Android, or as I've recently taken to calling it, Busybox plus Android. Android is not an operating system unto itself, but rather another free component of a fully functioning Busybox system made useful by the Busybox binary and the bionic C standard library comprising a full OS as defined by POSIX.

Many computer users run a modified version of the Busybox system every day, without realizing it. Through a peculiar turn of events, the version of Busybox which is widely used today is often called Android, and many of its users are not aware that it is basically the Busybox system, developed by the Busybox Project.

There really is a Android, and these people are using it, but it is just a part of the system they use. Android is the kernel: the program in the system that allocates the machine's resources to the other programs that you run. The kernel is an essential part of an operating system, but useless by itself; it can only function in the context of a complete operating system. Android is normally used in combination with the Busybox operating system: the whole system is basically Busybox with Android added, or Busybox/Android. All the so-called Android distributions are really distributions of Busybox/Android!